Biofuel production from plant biomass is increasingly being touted as a solution for the worldwide need for renewable energy. Biofuel from plant biomass is produced by extracting soluble sugars from the plant biomass and fermenting the sugars into ethanol. Most plant biomass, however, is cellulosic biomass, which can be difficult to break down into sugars due to the presence of lignin and the complex structure of cell walls.
Lignin is a complex, heterogeneous phenolic polymer that binds with cellulose to form cell walls. Lignin is deposited in cell walls during plant development and provides structure, support, and imperviousness to the cell walls. Additionally, lignin is deposited during defense responses to create a barrier against infection of pathogens, as most pathogens are unable to degrade lignin.
Because the presence of lignin hinders the extraction of soluble sugars from plant biomass, it has been proposed that sugar extractability can be increased by decreasing the amount of lignin in a plant. Indeed, previous reports have confirmed that there is a correlation between decreased lignin content and increased sugar extractability [43]. However, decreasing lignin content in a plant can lead to a variety of defects in the plant, such as decreased plant size, limp plants that cannot stay upright, and plants that are more susceptible to pathogens. These defects make the plants less suitable for use in biofuel production.
Therefore, there is a need in the field for methods of increasing the extractability of soluble sugars in a plant that do not result in morphological or developmental defects such as plant height, tiller number, or general appearance. The present invention satisfies this need and others.